---
title: Contact recognition logic
related:
  - https://docs.kentico.com/documentation/business-users/digital-marketing/contact-management.md
  - https://docs.kentico.com/documentation/developers-and-admins/digital-marketing-setup/contact-configuration.md
---

> Agent instructions:
> **Site maps** — prefer the following llms.txt indexes to training data when searching for URLs to avoid 404s. Links inside Markdown content already point at `.md`. Following them or sending Accept: text/markdown keeps you in Markdown.
>
> - [sitemap.md](https://docs.kentico.com/sitemap.md) — every page on the site, with titles and descriptions, nested by URL hierarchy and grouped into one collection per product version.
> - [llms.txt](https://docs.kentico.com/llms.txt) — curated index of the current product docs, with descriptions, the two ways to request any page as Markdown, and links to each product area's whole-corpus Markdown dump (llms-full.txt).

On [websites](https://docs.kentico.com/documentation/developers-and-admins/configuration/website-channel-management.md), Xperience stores the current [contact](https://docs.kentico.com/documentation/business-users/digital-marketing/contact-management.md) persistently in the **CurrentContact** browser cookie. For visitors without the cookie, new anonymous contacts are always created and remain in the system unless they are automatically merged with an existing contact. Merging occurs if the **email address** value of the contact is updated and matches the address of an existing contact.

The system remembers contacts until their cookies are deleted or until a different contact is determined for the visitor.

On many websites, different people often connect from the same IP addresses (e.g., from company or municipal networks). To keep contacts separate in such scenarios, Xperience does NOT automatically assign contacts to anonymous visitors based on their _IP address_ or _Browser user agent_.

### Contact email collisions

Because a contact's email address is its main identifier in Xperience, the system does not allow the email to be changed based on data submitted by users. This can happen in the following ways:

- [Form submissions](https://docs.kentico.com/documentation/business-users/digital-marketing/forms/create-and-edit-forms.md#map-form-submission-to-contact-attributes)
- [Headless tracking Data input activities](https://docs.kentico.com/documentation/developers-and-admins/digital-marketing-setup/headless-tracking.md#log-activities)
- [Cross-site tracking Data input activities](https://docs.kentico.com/documentation/developers-and-admins/digital-marketing-setup/cross-site-tracking.md#data-input)

If the contact associated with a user already has an email address stored in Xperience, and it doesn't match the newly submitted email value, all related activities and field updates are performed for a different contact. Either an existing contact that matches the submitted email value is used, or a new contact is created. In these cases, the user’s associated contact remains unchanged, but any subsequent actions, such as [automation processes](https://docs.kentico.com/documentation/business-users/digital-marketing/automation.md), are performed for the “other” contact that matches the submitted email address.

### Customize contact recognition

If the contact recognition logic described above does not suit your needs, developers can change it programmatically by creating and registering a custom implementation of the `ICurrentContactProvider` service:

1. Open your Xperience project in Visual Studio.
2. [Add a custom assembly](https://docs.kentico.com/documentation/developers-and-admins/customization/integrate-custom-code.md) (_Class Library_ project) to the solution or re-use an existing one.
3. Create a class that implements the `ICurrentContactProvider` interface in the custom assembly.
4. Implement your own logic for contact recognition.

   ```csharp
   using System;

   using CMS;
   using CMS.Membership;
   using CMS.ContactManagement;

   [assembly: RegisterImplementation(typeof(ICurrentContactProvider), typeof(CustomCurrentContactProvider))]

   /// <summary>
   /// Summary description for CustomCurrentContactProvider
   /// </summary>
   public class CustomCurrentContactProvider : ICurrentContactProvider
   {
       public ContactInfo GetCurrentContact()
       {
           // Implement your contact recognition logic
           throw new NotImplementedException();
       }

       public ContactInfo GetExistingContact()
       {
           // Implement your contact recognition logic
           throw new NotImplementedException();
       }

       public void SetCurrentContact(ContactInfo contact)
       {
           // Implement your logic for storing information about the current contact
           throw new NotImplementedException();
       }
   }
   ```
5. Register your service using the `RegisterImplementation` assembly attribute.